There has been made several proposals about a leather-like sheet having a natural dense feeling similar to that of natural leathers and a soft hand, which has a small difference in mechanical properties between the machine direction and the transverse direction and is moderately hard to elongate. For example, it has been reported that a leather-like sheet which has a soft hand and does not excessively elongate even under a large deforming stress to show an elongation limit is obtained by regulating the apparent density of substrate, the nonwoven fabric/elastic polymer mass ratio of the substrate, the thickness of grain layer, the load at 20% elongation (σ20)/load at 5% elongation (σ5) ratio in MD and TD of a leather-like sheet, etc. within a specified range (for example, Patent Document 1). However, since the proposed leather-like sheet is made of an entangled nonwoven fabric of short fibers, the entanglement between fibers gradually becomes loose upon elongation and the recovery is reduced. Therefore, shoes made of the proposed leather-like sheet by sewing become gradually wider during its wearing.
It has been attempted to reproduce the small stretchability and hand similar to those of natural leathers by forming the nonwoven fabric of the substrate layer from two layers with different finenesses (a layer of thicker microfine fibers and a layer of finer microfine fibers) so as to make a fineness gradient along the thickness direction, thereby imitating the natural leather structure (for example, Patent Document 2). However, since the proposed leather-like sheet is also made of an entangled nonwoven fabric of short fibers, the entanglement between fibers gradually becomes loose upon elongation and the recovery is reduced.
It has been attempted to produce a grain-finished artificial leather which combines a smoothness, a peeling strength and a hand with fullness by using a substrate composed of a nonwoven fabric made of bundles of microfine long fibers and an elastic polymer inside the nonwoven fabric (for example, Patent Document 3). However, the production method proposed merely intends to highly compact the bundles of microfine long fibers. Therefore, a leather-like sheet intended in the present invention has not been obtained, in which the ratio of mechanical properties between the machine direction and the transverse direction is nearly one.
In another proposed technique, a nonwoven fabric composed of 5 to 100 laminated fiber webs of accumulated continuous filaments each having a mass per unit area of 5 to 50 g/m2 is used so as to improve the compactness and flexibility of a long-fiber nonwoven fabric and reduce the unevenness of the mass per unit area of final products (for example, Patent Documents 4 and 5). However, the production method proposed addresses only the number of fiber webs to be laminated. Therefore, a leather-like sheet intended in the present invention has not been obtained, in which the ratio of mechanical properties between the machine direction and the transverse direction is nearly one.
Patent Document 1: JP 2003-13369A
Patent Document 2: JP 11-140779A
Patent Document 3: WO 2007/069628
Patent Document 4: JP 2003-336157A
Patent Document 5: JP 2004-11075A